Holding circuit control for reversible electric motors



March 28, 1950 L M P so s 2,502,023

HOLDING CIRCUIT 'CONTROL" FOR REVERSIBLE ELECTRIC MOTORS Filed Nov. 16,1946 L lM/T SW/ TCf/ES /6 mum: 60mm LIMIT smrcmfs smrcwss E ca/vmmINVENTOR Mfl/W/ CONTROL 19L ATTORNEYS.

Patented Mar. 28, 1950 HOLDING CIRCUIT CONTROL FOR REVERS- IBLE ELECTRICMOTORS Lawrence M. Persons, Chesterfield, M0., assignor to McQuay-NorrisManufacturing Company, St. Louis, Mo., a corporation of DelawareApplication November 16, 1946, Serial No. 710,325

.6 Claims. 1

This invention pertains to control apparatus of the character adaptedfor controlling reversible electric motors automatically in accordancewith Variations in quantities such as temperature and pressure. Theapplication is a continuation in part of my co-pending applicationSerial No. 437,672, filed April l, 1942, now abandoned.

In control systems for reversible electric motors, such as are employedin the adjustment of the cow] flaps of an aircraft motor and othercontrol dampers automatically in response to variations in circumambientor other temperatures, it usually happens that the temperature-sensitiveswitch is subject to vibration. In view of the fact that thetemperature-sensitive switch must be lightly constructed in order to besensitive to minute variations in temperature, it is, likewise,sensitive to vibrations of the installation. In situations where themotor is continuously under the control of such a temperature-sensitiveswitch the vibration of the latter results in frequent interruptions ofthe movement of the motor, due not to the movement of the switch inresponse to the desired controlling quantity, but, v, rather due to theundesired movement of the switch incident to the vibration.

The object of the present invention, generally stated, is to provide anautomatic control apparatus for aircraft engines and other vibrating,installations which is accurate, positive and de-" pendable in itsaction.

Another object is to provide such a control apparatus in which thetemperature or pressuresensitive switch, though subject to vibration,will. not, as an incident to such vibration, interrupt" operation of themotor.

Other objects will become apparent to those skilled in the art when thefollowing description is read in connection with the accompanyingdrawings in which:

Figure 1 is a circuit diagram illustrating the control apparatus of' thepresent invention;

Figures 2 and 3 are enlarged detail views showing, respectively, twodifferent positions of the motor-driven circuit interrupters shown inFig rections. The direction of operation is controlled by a temperatureor pressure-sensitive device operating through an arrangement ofswitches, interrupters and relays. The present invention ischaracterized by the feature that the temperature or pressure-sensitiveswitch, once actuated, is short circuited so that control of the motoris for the time being lost by it. Said short circuit is, however,periodically interrupted during the continued operation of the motor, sothat at intervals the sensitive switch regains control of the circuit.The invention is characterized by the further feature that neither thesensitive switch, nor the short circuiting control circuit about it, northe interrupter in the latter circuit is at any time required to conductpower currents for operation of the motor.

A further important feature of the invention resides in the provision ofan interrupter in the control circuit of such character that it willmomentarily break the control circuit at least once in each revolution,irrespective of the direction of rotation of the motor, and is soconstructed and arranged that, although the motor may stop at theinstant the circuit is broken by the interrupter, the latter willimmediately restore the circuit.

Referring now to Figures 1, 2 and 3 of the drawings for an illustrativeembodiment of the invention, a reversible electric motor I is providedfor driving a member, such as the cowl flaps of an aircraft engine (notshown), to be controlled. The motor I also drives one or moreinterrupters which may be of the character specifically shown in Figures2 and 3.

On a shaft 2, driven by the motor l, a conductor disc 3 is mounted, butseparated from the shaft by an insulation sleeve 4, so that duringrotation of the motor I the disc 3 is continuously rotating. The disc 3is provided with one or more notches 5. A spring contact 6 is arrangedto bear upon the periphery of the disc 3 in such a manner as to rideover notches 5 without losing contact. A second spring contact I alsobears at its end upon the periphery of disc 3. However, the lattercontact I is shortened so that its end will drop into the notches 5 asthey pass. During this drop, contact between the member I and the disc 3is lost momentarily and the circuit established between the contacts 5and l is open. Accordingly, a circuit depending upon an electricallybridged relation between the contacts 6 and 1 is interrupted momentarilyat every passage of one of the notches 5. In Figure 2 the dotted linepositions represent the dropping of the contact i into the notch as thedisc is turning in the counter-clockwise direction. Figure 3, on theother hand, illustrates the relation of the parts when the disc isturning in the clockwise direction.

The spring contact I is provided with a double bend, as illustrated, sothat upon reversal of the direction of rotation from that shown inFigure 3 to that shown in Figure 2, the end of the contact "I will dropinto the notch, as shown in full lines in Figure 3 in order to resumeits position at the 5 oclock station for rotation in the countercloclowise direction, as shown in Figure 2. During such a reversal of thedirection of rotation of the disc, compression of the double bend in thecontact I takes place.

In the embodiment shown in Figure 1, two such interrupters 3 and 3 areshown.

The reversible motor I is provided with field windings ii and 8' to beenergized, respectively, in accordance with the desired direction ofrotation of the motor. Power is supplied from a battery 9 through a leadID to a magnetic switch having contacts II and II. Arranged forselective contact with contact II is a lead i2 leading to field winding8, and, similarly, a lead iii leading to field winding 8' is arranged toselectively contact contact II.

The magnetic switch, to which. reference has just been made, is actuatedto close the circuit between contact I l and lead I2 upon energizationof coil I3 and to close the circuit between contact II and lead I2 uponenergization of coil iii.

In order to initiate the energization of the coils l3 and I3selectively, the invention contemplates either manual or automaticcontrol. In the case of automatic control, the manual switch 34 is movedto the station shown in Figure 1, which completes a circuit from thebattery 9 through conductor I5, switch I4, conductor iii, to a sensitiveswitch I! having a pair of contacts I8 and I3 selectively engageablewith conductors I9 and I9. It will be understood that the switch ii isactuated to make contact either at I8 or it or to stand open, dependingupon the position indicated by the index member 20, which may be athermally responsive member, a pressure responsive member or responsiveto some other controlling quantity. When the index member 20 has movedswitch ill to the position whereat a circuit is completed from contactI8 to conductor IS, the magnetic switch coil I3 is energized. Thiseiiects a closure of the circuit between contact I i and conductor I2,and, at the same time, eiiects a closure of a holding circuit fromauxiliary contact iii to conductor 22 and through interrupter 3 to coilI3. Once this holding circuit is completed, the sensitive switch I1 maychatter or vibrate without interrupting the flow of current through coilI3, and without interrupting the flow of current through the powercircuit to the motor, except, as in the rotation of interrupter 3, amomentary interruption of the holding circuit may coincide with themomentary interruption at switch II. While the energization of the coilI3 is initiated by a closure of contacts at switch I'I, once themagnetic switch is actuated to close contacts I I and 2!, such contactsare free from control by switch I'I, until the holding circuit isinterrupted by interrupter 3. At the instant of such inter-- ruptioncontrol of the circuit is restored to the sensitive switch I I.

If, on the other hand, the index member 26 moves to close the circuitfrom contact ill to conductor I9, then coil I3 of the magnetic switch isenergized to effect a closing of the power circuit across contact II andconductor I2 and, concurrently to complete a holding circuit fromauxiliary contact 2| through conductor 22', interrupter 3 and coil l3.

For manual operation of the circuit shown in Figure 1, the switch memberI4 is moved to station for energization of coil I3 and motor fieldwinding 8, or to station 23' for energization of coil I3 and motor fieldwinding 8'.

In the embodiment shown in Figure l, the parts are identical with thatshown in Figure i, save that a single interrupter 43 is provided insteadof the two interrupters 3 and 3 shown in Figure 1. In this instancethere is a complete interruption of the flow of current through themagnetic switch coil and a complete interruption of the flow of currentto the motor upon each interruption at the interrupter 43, but, due tothe character of the interrupter, the circuit is immediately restored.

Referring now to Figure 5 for a further embodiment of the invention, themotor I drives a single interrupter 53, in addition to the controlledmembers designed to be driven by it. As in the previous embodiment, thepower circuit to the motor is directionally controlled by a magneticswitch having two sets of main contacts 5i and SI arranged,respectively, to control the circuit to field windings 8 and 8. Themagnetic switch is also provided with auxiliary contact 54 arranged forengagement with a stationary contact 55 when the main contacts 5i are inengagement with their stationary contacts. Likewise, auxiliary contact Mis arranged for engagement with the stationary contact 55' when the maincontacts 5i are in engagement with their stationary contacts. Moreover,a further set of auxiliary contacts and 56 are arranged to engagestationary contacts 55 and 55 selectively, it being understood that thebars carrying contacts 5|, 54 and 55 all tilt in the same directionconcurrently.

In order to actuate the magnetic switch so as to close main contacts 5|,coil 51 is energized. This is accomplished through a sensitive automaticswitch 58, as before. Upon initial en rgization of coil 51, the magneticswitch is closed to complete the power circuit across contacts 5i, aswell as to complete a holding circuit between contacts 54 and 55. Uponthe completion of the latter circuit, which involves short circuitingthe switch 58 through interrupter 53. control of the circuit is lost bythe sensitive switch 58 and not resumed until a momentary interruptionoccurs at interrupter 53.

For operation of the motor in the oppo ite direction, coil 5'! of themagnetic swiich is energized to complete the power circu t acrosscontacts 5| and concurrently complete a holding circuit across contacts54' and 55' through interrupter 53.

In situations where the motor I may have operated to such extent in onedirection. (as for example with contacts 5| closed) that the limitswitch opens. it will be apparent that, although the motor isdisconnected from the source of power, the control circuit remainsenergized and the holding circuit remains complete, because theinterrupter 53 is no longer turning. When. during the prevalence of sucha situation, the sensitive switch 58 moves so as to close the op ositecircuit both coils of the magnetic switch. 51 and 51, would be energizedbut for the fact of the grounding connection through contacts 56 and56'. When coil 51 is energized, contact 56' engages contact 55 to groundthe side of the sensitive switch 58 which leads to coil 51'.Consequently, when the switch 58 moves to complete the circuit on theside of coil 51' (the circuit through coil 51 standing complete throughinterrupter 53) a short circuit to ground is produced which deenergizescoil 51 and releases the magnetic switch with concurrent interruption ofthe short circuit to ground through contacts 55" and 56' so that coil51' may now be energized. When the motor is operated to its limit in theopposite direction, the same sequence of operations occurs, but with theopposite contacts.

From the foregoing description, those skilled in the art should readilyunderstand the arrangement and operation of the control apparatus andcircuit, and realize that the invention permits the utilization of ahighly sensitive automatic control switch without rendering operation ofthe motor subject to irequent interruption as an incident to thechattering of the contacts at the magnetic switch. Such is accomplishedin the embodiments of Figures 1 and 5 by providing a short circuit aboutthe sensitive switch and locating in said short circuit an interrupterwhich periodically and instantaneously breaks the short circuit duringthe continued operation of the motor, and thus restores control to thesensitive switch.

It will be understood that, while several embodiments of the circuithave been illustrated, the invention is not limited to the detailsthereof, nor to the specific type of interrupter employed. It is,therefore, to be distinctly understood that many modifications andvariations may be made consistent with the foregoing disclosure andwithout departing from the spirit of the invention, or of the scope ofthe appended claims.

Having thus described the invention, what is claimed and desired to besecured by Letters Patent is:

1. Control apparatus of the character described, comprising, acontrolled element, reversible electrical operating means therefor, anindex member actuated in accordance with variations in the controllingquantity, contact means actuated by said index member to close thecircuit of said operating means, a locking circuit paralleling thecircuit of said operating means for holding said contact means closed,and means driven by the reversible electrical operating means andoperating periodically to momentarily interrupt said locking circuitregardless of the posi tion of the index member, and regardless of thedirection of operation of the electrical operating means.

2. Control apparatus of the character described, comprising, acontrolled element, reversible electrical operating means therefor, anindex member actuated in accordance with variations in the controllingquantity, a relay actuated by said index member to close the circuit ofsaid operating means, a holding circuit for said relay paralleling thecircuit of said operating means, energized upon closure of sand circuitto hold the circuit closed, and said holding circuit including meansdriven by said electrical operating means and operating periodically tode-energize said holding circuit regardless of the direction ofoperation of said reversible electrical operating means.

3. Control apparatus for a reversible electric motor having a powercircuit, a magnetically operated switch having contacts arranged todirectionally control energization of said motor from. said powercircuit, said switch having operating coils connected in a controlcircuit paralleling said motor irrespective of; whether said magneticswitch is open or closed, said control circuit including a switchsensitive to variations in a contro ling quantity for selectivelyinitiating energization of said switch operating coils, and a holdingcircuit shunting said sensitive switch and including an interrupterdriven by said motor for periodically breaking the holding circuitduring operation of the motor, said holding circuit including contactsassociated with said magnetically operated switch and actuated betweenopen and closed positions as said magnetically operated switch moves tomake and break the power circuit to said motor.

4. Control apparatus for a reversible electric motor having a powercircuit, a magnetically operated switch having contacts arranged todirectionally control energization of said motor from said powercircuit, said switch having operating coils connected in a controlcircuit paralleling said motor irrespective of whether said magneticswitch is open or closed, said control circuit including a switchsensitive to variations in a controlling quantity for selectivelyinitiating energisation of said switch operating coils, and a holdingcircuit shunting said sensitive switch and including an interrupterdriven by said motor for periodically breaking the holding circuitduring operation of the motor, irrespective of the direction of rotationof said motor, said holding circuit including contacts associated withsaid magneti-cally operated switch and actuated between open and closedpositions as said magnetically operated switch moves to make and breakthe power circuit to said motor.

5. Control apparatus for a reversible electric motor having a powercircuit, a magnetically operated switch having contacts arranged todirectionally control energization of said motor from said power circuitand auxiliary contacts arranged to control energization of a holdingcircuit, said switch having operating coils connected in a controlcircuit paralleling said motor irrespective of whether said magneticswitch is open or closed, said control circuit including a switchsensitive to variations in a controlling quantity for selectivelyinitiating energization of said switch operating coils; a circuitinterrupter consisting of a conductor disc mechanically driven by saidmotor and a pair of brushes riding the periphery of said disc, one ofsaid brushes connected to the control circuit between the sensitiveswitch and the coil of the magnetic switch and the other of said brushesconnected through said auxiliary contacts to the opposite side of thesensitive switch, said conductor dis-c having a peripheral indentationproportioned to momentarily break contact with one of said brushes asthe indentation passes said brush.

6. Control apparatus for a reversible electric motor having a powercircuit, a magnetically operated switch having contacts arranged todirectionally control energization of said motor from said powercircuit, said switch having operating coils connected in. a controlcircuit paralleling said motor irrespective of whether said magneticswitch is open or closed, said control circuit including a switchsensitive to variations in a controlling quantity for selectivelyinitiating energization of said switch operating coils, a holdingcircuit shunting said sensitive switch, said holding circuit includingcontacts associated with said magnetically operated switch and actuatedbetween open and closed positions as said REFERENCES CITED magneticallyoperated switch moves to make and break the power circuit to said motor,and an g i j i are of record m the interrupter driven by said motor forperiodically p momentarily interrupting the holding circuit 5 UNITEDSTATES PATENTS irrespective of the direction of rotation of the NumberName Date 1 703 634 Tannehill Dec. 2 1930 LAWRENCE PERSONS- 2,077,086Adair Apr. 13, 1937

